The invention described in the present disclosure relates to plant for the treatment of drinking water from raw water, in accordance with the general terms set forth in patent claim 1.
The provision of drinking water that meets all quantitative and qualitative criteria is a worldwide problem whose solution is an important aspect of the basis of civilization as a whole.
Developing countries generally suffer from lack of water, particularly drinking water. On the one hand, this is due to the fact that the amount of water available is limited because of soil conditions and climate; on the other, because the means of water treatment and distribution are either lacking or supply water of inadequate hygienic quality.
Where water-distribution systems are scarce or non-existent, water is usually supplied from storage systems, such as groundwater or rainwater cisterns, or from large storage tanks refilled from time to time by tanker vehicles.
But general overuse of resources and the environmental pollution associated with it has also made the provision of an adequate supply of drinking water a problem in industrialized countries. Although densely populated regions in industrialized countries have water-distribution systems equipped with water-treatment plants, the quality of the water supply often only barely meets hygienic requirements or is no longer adequate for them, or the water tastes unpleasant because disinfectants and/or other chemicals have been added to it. And because of defects such as broken conduits and leaks, the distribution system itself also represents a constant risk of further water pollution.
Because of all these problems, there is a growing need of plant that can treat raw water and turn it into drinking water for domestic use. The raw water for such small systems can be supplied from small local springs, groundwater or rainwater cisterns, or by mains that otherwise fail to provide water of satisfactory quality. This type of plant makes use of various types of treatment process, for example by filters that remove larger particles, by reverse-osmosis equipment for desalination, and by activated-carbon filters for final purification, which may be used either separately or in series, as necessary. In order to obtain a hygienically satisfactory quality of water, ozone treatment of water has now for some time replaced the chlorination process usual in the past. Ozone treatment, in the literature also referred to as ozonization, is performed by the addition of active oxygen (ozone =O.sub.3) to carbon. Except for fluorine, ozone is the strongest oxydizing medium known. It permits practically total neutralization of micro-organisms without making the water taste unpleasantly of chlorine. Ozone is in fact said to have a pleasant smell reminiscent of hay or wet grass after a summer thunderstorm.
Moreover, ozone is a relatively cheap oxydizing agent. To produce it, some O.sub.2 molecules in the ambient air are split into oxygen atoms, which then combine with the remaining O.sub.2 molecules to form O.sub.3 molecules. Further, ozonization produces no undesirable waste materials, because ozone tends to break down again into O.sub.2. Though ozone can in fact attack the human body, it is possible to avoid such an undesirable effect either by the total prevention of residual ozone in the drinking water, or by keeping it to a minimum or in a safe predetermined concentration.